1. Field of the Invention
The present invention relates to fluid storage towers for a cooling system. More specifically, the invention provides a pipe-coil arrangement for a cylindrical ice-thermal storage tower facility with a phase-change fluid, which storage facility is usually vertically arranged on a relatively compressed land parcel. The pipe-coil arrangement is configured to fill a geometric sector of a tower, which sector is a portion of a circular cross-section in a plan view. Use of a plurality of such pipe-coil arrangements for several such tower sectors cooperate to fill a planar cross-section, usually a circle, of a tower. A plurality of individual coils of the present invention may be vertically arranged in stacks and used in lieu of present rectangular or oblong storage coil configurations. The stacked coils will more completely or more efficiently fill the available tower volume than the rectangular coils, thereby more completely using the available internal storage volume of a cylindrical tower. The phase-change fluid in the tower volume, generally water, may be solidified into a thermal storage mass by the coolant fluid transferred through the pipe coils.
The solidification process is associated with a change in temperature and volume of the storage phase-change fluid, that is expansion and contraction between the liquidus and solidus states and, related structural expansion-contraction and operational problems of the tower. The shaped pipe-coil arrangements noted above are generally triangular or wedge-shaped in a plan view. Utilization of several of the wedge-shaped sections collectively operate to occupy and thus more completely utilize the cross-sectional area of the cylindrical tower. Consequently the available tower volume is more completely filled, which provides a more efficient use of the available thermal storage capacity of an ice-thermal storage tower structure.
2. Prior Art
Cooling towers are frequently utilized in cooling and air conditioning apparatus. These tower apparatus may include condensers, evaporators or water towers. Further, tall vertical towers with circular cross-sections are known and used in the water or liquid storage industry. However, tower structures are not generally used in an ice-thermal storage apparatus, or rather, the height of the structure has been limited to a relatively low height. In particular, it is known that ice-thermal storage towers have been, or are usually, constructed with a maximum height or vertical limitation of six heat exchange coil sections, or stacks, in height, which limit may be considered to be approximately forty feet in vertical elevation. The historic background to this limitation is not specifically known, however, the land mass available for ice thermal storage units has induced their assembly in a laterally expansive or horizontal direction rather than as a vertical structure. Thus, the generally available ice-thermal storage units, their structure and capacity have been, or are known to be, limited to a collection of heat exchange thermal storage coils only six units, or stacks, in height. The assembled plurality of heat exchange coil units is often serially arranged in a horizontal manner, which units are usually factory-assembled coil modules. This historical assemblage of thermal-storage units allowed ease of construction and maintenance, but did not maximize the vertical usage of available land mass.
A known ice thermal storage structure, which is approximately twenty-five feet high, has a diameter less than twelve feet. In this known structure, the cooling coil segments of the tower are annuli with a height of approximately four feet. These coil annuli are manufactured in an assembly plant and thereafter site-assembled. However, the noted dimensional limitations are shipping constraints imposed by freight transport capacities and capabilities. Therefore, the tower structure is limited both in height and diameter.
Ice-thermal storage units are utilized in a variety of applications, such as commercial office buildings, schools and hospitals. Ice thermal storage technology has evolved as a comparatively economical, energy conserving means to store cooling capacity, which cooling capacity is developed and stored during a time period when energy costs are more economic. As an example, ice is developed or generated during the night when both electric rates and consumer demand are lower than during the day. The cooling capacity of the stored ice is usually utilized during higher demand and higher electric rate periods to provide cooling for commercial facilities, such as office buildings, schools, hospitals and banks.
The operational mode of an ice-thermal storage unit is dependent upon the type of equipment and its application. The ice-thermal storage units usually provide a phase-change fluid, such as water, in a storage housing with a plurality of heat exchange coils or coil sections immersed in the phase-change fluid. The heat exchange coils are coupled to a refrigerant circuit for communication of a refrigerant coolant fluid through the coils. The refrigerant fluid cools the phase-change fluid and develops ice on the heat exchange coils in the storage housing during the cooling cycle. This ice develops around the heat exchange coils until essentially all the phase-change fluid in the tank is either a crystalline solid, that is ice, or is at, or about, the fluid freezing point. Thereafter, the ice mass is retained until a demand or load is applied to the ice mass, such as by coursing warm phase-change fluid over the heat exchange coils and the ice in the tower. Alternatively, a warm coolant fluid could be transferred through the coils for reducing its temperature. The warm fluid is reduced in temperature and may be transferred to a warm load, such as a heat exchanger, evaporator, condenser, subcooler, or another application requiring a reduced temperature refrigerant or working fluid. This temperature reduction of the warm phase-change fluid melts at least some of the ice mass and, depending upon the demand or load, will eventually elevate the temperature of the stored phase-change fluid in the tower above the melting-freezing temperature. Alternatively, it is possible to utilize the chilled fluid in the tank to cool an ancillary operating unit. The cooling or freezing cycle is then iterated to again generate frozen fluid for harvesting of the stored cooling capacity at a later time.
An exemplary and known large mass ice-cooling thermal storage system is located in a metropolitan area and is operable to provide chilled water for numerous buildings in a commercial district. This system includes a plurality of serially arranged, large ice thermal storage units in a central location, which units are individual, free-standing units on separate levels or building floors. The collection of units has a facade structure around its skeleton to mask the operating equipment. However, this assembly or system is not a single, multistory tower for retention of all the phase-change fluid, and it does not have a plurality of heat exchange coil segments retained within a single tower. The particularly noted, centrally located chilled water system is operable and adaptable to a downtown metropolitan environment because of the relatively close proximity of a large number of users of chilled water.
Single large-volume ice thermal storage units are known but they are generally low-profile or low-height, horizontally arranged assemblies of multiple ice-thermal-storage units distributed over a broad area, that is only up to six heat exchange segments in height, but either very wide or very long. These are not vertically projecting structures on a relatively small surface area footprint. An exemplary thermal storage unit is illustrated in U.S. Pat. No. 4,831,831 to Carter et al. The necessary piping, manifolds, couplings and valves for arranging a plurality of either vertical or horizontal units are not shown therein, but these elements are known in the art.
An ice-thermal storage unit may have a fixed latent storage capacity in terms of cooling ton-hours, as well as specified coolant fluid flow rates and prescribed inlet and outlet temperatures. The storage unit, which may have specific dimensions and an operating mass or weight, can include a tank, a coil, insulation, exterior panels, a cover or covers, an air pump and an air distributor.
There are a number of operating modes associated with the use of thermal storage units, which modes may typically include the following: (1) ice build-up; (2) ice build-up with cooling of the coupled cooling load; (3) cooling utilizing; the ice only; (4) cooling with a chiller only; and, (5) combined cooling with both a chiller and the ice. The present invention is available to provide all of the noted operations; to be coupled to a plurality of users or cooling loads remote from the situs; and, to occupy a minimal land mass while providing a large capacity ice thermal storage facility.